Elsevier

The Lancet

Volume 363, Issue 9404, 17 January 2004, Pages 185-191
The Lancet

Articles
Sudden unexplained infant death in 20 regions in Europe: case control study

https://doi.org/10.1016/S0140-6736(03)15323-8Get rights and content

Summary

Background

After striking changes in rates of sudden unexplained infant death (SIDS) around 1990, four large case-control studies were set up to re-examine the epidemiology of this syndrome. The European Concerted Action on SIDS (ECAS) investigation was planned to bring together data from these and new studies to give an overview of risk factors for the syndrome in Europe.

Methods

We undertook case-control studies in 20 regions. Data for more than 60 variables were extracted from anonymised records of 745 SIDS cases and 2411 live controls. Logistic regression was used to calculate odds ratios (ORs) for every factor in isolation, and to construct multivariate models.

Findings

Principal risk factors were largely independent. Multivariately significant ORs showed little evidence of intercentre heterogeneity apart from four outliers, which were eliminated. Highly significant risks were associated with prone sleeping (OR 13·1 [95% CI 8·51–20·2]) and with turning from the side to the prone position (45·4 [23·4–87·9]). About 48% of cases were attributable to sleeping in the side or prone position. If the mother smoked, significant risks were associated with bed-sharing, especially during the first weeks of life (at 2 weeks 27·0 [13·3–54·9]). This OR was partly attributable to mother's consumption of alcohol. Mother's alcohol consumption was significant only when baby bed-shared all night (OR increased by 1·66 [1·16–2·38] per drink). For mothers who did not smoke during pregnancy, OR for bed-sharing was very small (at 2 weeks 2·4 [1·2–4·6]) and only significant during the first 8 weeks of life. About 16% of cases were attributable to bed-sharing and roughly 36% to the baby sleeping in a separate room.

Interpretation

Avoidable risk factors such as those associated with inappropriate infants' sleeping position, type of bedding used, and sleeping arrangements strongly suggest a basis for further substantial reductions in SIDS incidence rates.

Introduction

The remarkable increase in sudden unexplained infant death (SIDS) rates recorded, especially in Norway1 and in several other countries,2, 3, 4 towards the end of the 1980s prompted large scale case-control studies that were set up during 1992 in Scandinavia,5 Ireland,6 England, and Germany.7, 8 The succeeding reduction in SIDS rates, led by the Netherlands,9 which occurred in some countries necessitated a reassessment of risk factors for the syndrome because, despite the reductions, SIDS was still a major cause of infant mortality after the first week of life. These investigations all included similar questions about most previously established risk factors. At the 1992 meeting of the European Society for the Study and Prevention of Infant Death, participants suggested the potential value of integrated data from these and other studies, which led to the founding of the European Union Concerted Action on SIDS (ECAS) in January, 1994. Our main aims were to combine data from across Europe and thereby establish risks currently associated with previously suspected risk factors, especially those associated with infant care practices, assess whether levels of risk vary across Europe, and investigate the extent to which risk factors interact.

Section snippets

Methods

In addition to continuing research, new studies that all followed the same ECAS protocol were set up in 12 centres, six of which were in eastern Europe. Therefore, data were derived from case-control studies of SIDS of varying duration done in 20 centres between September, 1992, and April, 1996. Denmark, Norway, and Sweden, which comprised the Nordic study, were counted as three centres, as were the three regions (Yorkshire, Trent, and South West)that made up the first 2 years of the

Results

20 European centres assembled data for 745 cases of SIDS and 2411 controls (table 1). 12 new centres using the ECAS protocol contributed 138 (19%) cases. For the 20 centres, SIDS incidence rates at the time of the studies ranged from 0·17 per 1000 in Hungary to 1·3 per 1000 in Nordrhein-Westfalen (median 0·6 [IQR 0·4–0·7]). Seasonal rates varied by 13·6% (3·3%–26·1%) either side of the mean (p=0·018) with peak incidence close to the shortest day. Although frequency was higher at the weekend

Discussion

Across the centres, the ORs for sleeping prone was negatively correlated with the prevalence of this sleeping position.17 Thus, our OR was much higher than noted in earlier investigations when sleeping prone was much more common.

Adjusted OR for position the infant was last left inside versus supine—was not significant. However, the side position was much less stable than the back position. During the controls' reference sleep, 61% who were left on their side moved compared with 12% controls

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